## Description

When a model group (identified by `model_name`) has multiple deployments (e.g., same model from different providers like Azure OpenAI vs OpenAI, or multiple vLLM instances), operators need a simple way to **hot-switch which deployment is the "active" one** from the Admin UI — similar to a "CC Switch" experience.

## Current state

The closest existing feature is the **Pause/Resume Switch** (PR #27927, #28151, closed issue #13703). This allows pausing individual deployments from the UI, and traffic automatically routes to sibling deployments under the same `model_name`. However, the UX is different from a dedicated active-backend selector:

- Pause/Resume is a binary on/off toggle per deployment - It does not visually show "this deployment is currently the active one" vs "this is a standby" - Switching requires pausing one deployment and relying on fallback, rather than explicitly selecting which deployment should handle traffic

## Desired functionality

A dedicated UI component that:

1. **Groups deployments by model group** — shows all deployments under a given `model_name` 2. **Displays deployment metadata** — provider, model, api_base, order, health status 3. **…